This invention relates to a technique for paging to a mobile terminal in a wireless communication system in which the location registration area required for location registration is set automatically.
The problem in a mobile communication system is how to suppress the battery consumption of the mobile terminal. In order to suppress the battery consumption, the mobile terminal moves in a state (standby mode) with the communication disconnected with the base stations while not in data communication. In the case where the data terminates at a mobile terminal in standby mode, the mobile communication system, not informed of the location of the mobile terminal, is required to send the call signal from a plurality of base stations. The transmission of a call signal from a multiplicity of base stations in response to the data termination at a single mobile terminal is the waste of the wireless resources. In order to suppress the waste of the wireless resources due to the call signal, a technique called the location registration to specify a certain range of base stations associated with the mobile terminal is disclosed in 3GPP (3rd generation partnership project) 3GPP TS 24. 301 V1.0.0 and 3GPP (3rd generation partnership project) 3GPP TS 23. 401 V8.3.0. which are standard documents describing the technical specifications in LTE (Long Term Evolution) system providing the 3.9-generation wireless communication technology.
These documents 3GPP (3rd generation partnership project) 3GPP TS 24. 301 V1.0.0 and 3GPP (3rd generation partnership project) 3GPP TS 23. 401 V8.3.0. describe a location registration method using a location registration area called the tracking area (TA) configured of a plurality of base stations. A call processing control unit discriminates the TA with an area identifier called TAI (Tracking Area Identity). TAI is allocated to all the base stations, and the same value of TAI may be allocated to a plurality of base stations. The area in which a mobile terminal exists is managed by TAI. In the case where a mobile terminal is managed in one TAI area, however, the call page message is sent to only one TAI area, and therefore, the consumption of the wireless resources used for the incoming call can be suppressed. The management of a mobile terminal in one TAI area, however, requires the location registration each time the mobile terminal moves to the area of a different TAI, resulting in an increased consumption of the wireless resources due to the location registration process. A method to suppress the increased consumption of the wireless resources due to the location registration process by managing the mobile terminal using a location registration area identifier list (TAI list) containing a plurality of TAIs is described in 3GPP (3rd generation partnership project) 3GPP TS 24. 301 V1.0.0 and 3GPP (3rd generation partnership project) 3GPP TS 23. V8.3.0.
In the case where the TAI list having a plurality of TAIs is used, the mobile terminal ceases to execute the location registration process at the time of moving within an area associated with the TAI contained in the TAI list. Therefore, the location registration process is executed less frequently, thereby making it possible to suppress the increased consumption of the wireless resources due to the location registration process. The information contained in the TAI list of the mobile terminal is updated at the time of the initial attachment (initial connection process) and at the time of executing the location registration process (TAU: tracking area update) started from the mobile terminal moving into an area of a TAI not contained in the TAI list. The base station periodically transmits, as the notification information, the TAI information associated with itself to the mobile terminal. The mobile terminal, by checking the TAI contained in the notification information transmitted from the base station, grasps which TA it is currently located in. In the case where the data terminates at the mobile terminal in standby mode with the TAI list of the mobile terminal managed by the call processing control unit, the call processing control unit judges that the mobile terminal in standby mode is located in an area corresponding to the TAI list, and requests the base stations in the area of the TAI list to notify the mobile terminal that the data has terminated at the mobile terminal. In the case where the location registration process is executed each time the mobile terminal moves between base stations, the call processing control unit can specify one base station as the location range of the mobile terminal in which the mobile terminal is controlled by the particular base station, and therefore, the amount of the wireless resources used for the call notification can be minimized. In the case where the location registration process is executed each time all the mobiles move between base stations, however, the location registration message is sent each time the mobile terminal moves between stations, and therefore, the location registration process is executed more frequently, thereby increasing both the consumption of the wireless resources and the power consumption of the mobile terminal. As a result, how the area (the area corresponding to the TAI list) for which the location registration process and the data termination process are executed is to be determined poses a problem to be solved for system optimization.